1. Field of the Invention
The present invention relates to a visual function test apparatus for examining visual functions of an examinee""s eye.
2. Description of Related Art
A contrast sensitivity test in which optotypes of different contrasts are presented to an examinee has been performed as one of visual function tests. This contrast sensitivity test is important for examination of a visual function, in particular, a form sensitivity ability. A chart used in a conventional test for contrast sensitivity is constructed of a panel such as paper on which stripes with different frequencies, in several kinds of contrast ratios, are drawn. Furthermore, the contrast sensitivity test is conducted using an apparatus designed specifically therefor.
The chart made of a paper panel or the like, which is large as a whole, requires a large space sufficient to put up the chart on a wall or the like. Since the chart is used as put up an the wall or the like, the test is susceptible to ambient light.
Moreover, the apparatus designed specifically for contrast sensitivity test is not sufficiently provided with other visual acuity test systems. To make various kinds of visual function tests with respect to an examinee""s eye, an optometer and other devices need separately preparing. In this case, an additional space is required to place the plural devices, which may make the test troublesome.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a visual function test apparatus that is space-saved and capable of examining plural visual functions such as a contrast sensitivity test, a visual acuity test, on a standalone basis.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided a visual function test apparatus for testing a visual function by presenting an optotype to an examinee""s eye, the apparatus including: a first half mirror disposed on a projection optical axis of light of the optotype; an illumination light source having a projection optical axis which is made substantially coaxial with the projection optical axis of the optotype light by the first half mirror; a concave mirror which reflects an illumination light from the illumination light source and the optotype light; a second half mirror disposed between the first half mirror and the concave mirror, the second half mirror reflecting the optotype light and the illumination light both reflected by the concave mirror toward the examinee""s eye; and a control section which changes a ratio between a light quantity of the optotype light and a light quantity of the illumination light in accordance with a predetermined contrast ratio.
According to another aspect of the present invention, there is provided a visual function test apparatus for testing a visual function by presenting an optotype to an examinee""s eye, the apparatus including: a concave mirror which reflects light of the optotype; a half mirror which reflects the optotype light reflected by the concave mirror toward the examinee""s eye; an illumination light source having a projection optical axis which is made substantially coaxial with a projection optical axis of the optotype light by the half mirror; and a control section which changes a ratio between a light quantity of the optotype light and a light quantity of an illumination light from the illumination light source in accordance with a predetermined contrast ratio.